Individual tooth element for broach

ABSTRACT

The present invention presents individual interlocking cutting elements which are adapted to be combined in an interdependent relationship to create a form broach. Each individual cutting element is adapted to interlock with a neighboring cutting element by a male and female V-groove interlock structure which forms a part of each tooth.

United States Patent Schmidt 51 May 16,1972

[54] INDIVIDUAL TOOTH ELEMENT FOR BROACI-I [72] Inventor: Frederick W. Schmidt, 19 Windmill Hill Road, Branford, Conn. 06405 [22] Filed: Feb. 2, 1970 [21] Appl. No.: 7,960

Related U.S. Application Data [63] Continuation of Ser. No. 716,919, Mar. 28, 1968.

[52] U.S. Cl ..29/95.1

51 Int.Cl ..B26d 1/04 [58] FieldoiSearch ..29/95,95.l,96,97

[56] References Cited UNITED STATES PATENTS 2,585,832 2/1952 Phaneuf ..29/95.1

2,855,656 10/1958 Poynter ....29/95.l 2,964,833 12/ 1960 Novkov ..29/95 FOREIGN PATENTS OR APPLICATIONS 890,1 14 2/1962 Great Britain ..29/95.l 147,428 1965 U.S.S.R. ..29/95.l

Primary Examiner-Harrison L. Hinson AttorneyFishman and Van Kirk [57] ABSTRACT The present invention presents individual interlocking cutting elements which are adapted to be combined in an interdependent relationship to create a form broach. Each individual cutting element is adapted to interlock with a neighboring cutting element by a male and female V-groove interlock structure which forms a part of each tooth.v

9 Claims, 6 Drawing Figures INDIVIDUAL TOOTH ELEMENT FOR BROACI-I CROSS-REFERENCE TO RELATED APPLICATION:

This application is a division of my U.S. Pat. application Ser. No. 716,919 tiled Mar. 28, 1968.

BACKGROUND OF THE INVENTION:

1. Field of the Invention This invention relates to broaching tools. More particularly, this invention relates to an individual tooth element for multiple tooth form broaches particularly adapted for broaching slots, openings or channels of specialized cross section. The invention is particularly useful for teeth for forming the socalled Christmas tree grooves in turbine discs which are used to mount similarly shaped turbine blade roots, but it will be clearly understood that the invention is not limited to forming such grooves.

2. Description of the Prior Art The traditional prior art broaching tool has been a sticktype broach in which a number of broaching teeth or teeth sets are formed on a single solid stick. A number of particularly troublesome problems directly attributable to the unitary stick-type construction have been present in the manufacture, use and service of these traditional prior art stick-type broaches. By way of illustration of some of these problems, in the machining operation of the stick-type broaches large machines and extensive setups are required, and the machinery must have the capability of turning out stick-type segments of various lengths. In the heat treat operation in the manufacture of stick-type broaches a large amount of warpage is encountered due to the extensive length of the stick; cracking occurs resulting in the loss of the entire stick; and nonuniform heat treatment results due to the excessive length of the stick. In the grinding operation in the manufacture of stick-type broaches excessive grinding wheel breakdown is encountered due to the length of the stick, and small diameter wheels must be used for backoff thus leading to excessive wheel breakdown. In the assembly operation in the manufacture of sticktype broaches the quality of the overall stick form is a direct result and function of the operators skill in forming the entire stick, with the quality of the stick being only as good as the worst tooth, and an undersized tooth results in an overloading, sometimes severly, of the next tooth. In the servicing operation in the use of stick-type broaches a substantial undersizing of a tooth, through wear or otherwise, makes it necessary to discard the entire stick even though there is still useful life left in many or all of the other teeth, and the entire stick is also last as the result of any tooth damage or crack up with respect to any one tooth or any one part of the stick. The choice of materials from which stick-type broaches have been made has also been restricted by the stick configuration. High-speed steel has been used, but never carbide because carbide is so expensive that a mistake could not be tolerated in forming a stick from a large piece nor could the loss of the entire too] be tolerated because of the failure of one tooth.

Attempts or suggestions have been made in the prior art to overcome some of these deficiencies in the traditional broach structure by forming a broach assembly from several broaching segments, each segment having several teeth; and suggestions have also been made to form a broach from individual teeth inserted in a holder. However, these suggestions have proven to be impracticable for a variety of reasons, principal among which have been that they have lacked the necessary stability for broaching operations and have been particularly susceptible to winking wherein the front ends of the teeth move from side to side because of pressures on the tool.

SUMMARY OF THE INVENTION:

The present invention presents individual teeth with a V- groove interlock structure which may be asembled together to form a broach. Each tooth has a V-shaped projection on either the top or bottom surface thereof, and the other surface is provided with a correspondingly angled V-shaped notch or recess. The teeth are intended to be assembled one upon the other to construct a form broach whereby the protrusions and notches on adjacent teeth interlock, and the assembly may be concluded with end structure and a tie rod passing through the base of the interlocking teeth. This construction, especially the interlocking teeth, overcomes the deficiencies encountered in the previously suggested segmented broaches thus making possible, for the first time, a practicable individual tooth segmented broach assembly which overcomes the numerous disadvantages of a stick-type broach. Considering the aspects of manufacture, use and service previously discussed with respect to the traditional stick-type broach, the individual teeth of the present invention for a segmented broach offer numerous advances and improvements in the step of machining in the manufacture of the individual teeth; small machines can be used to turn out the individual teeth, the machines being of the type which can be automated, and all of the individual teeth can be initially cast or otherwise formed of uniform size and then ground to size in the putting area. In the heat treat operation in the manufacture of the broach formed from the individual teeth, stick warpage is eliminated since there is no long stick to heat treat; cracking means loss of a single tooth only; and a uniform heat treat can be quality controlled for the small individual teeth. In the grinding operation in the manufacture of the individual teeth, wheel breakdown is controlled because only one tooth is being ground at a time, and large diameter wheels can be used for backoff because there is no adjacent tooth to run into, thus resulting in reduced frequency of wheel breakdown. In the assembly operation in the manufacture of a broach with the individual teeth, great selectivity can be employed in the choice of the best teeth to be used as finishers, and undersized teeth can either be eliminated or selectively placed at the start of the broach to essentially eliminate overloading due to undersizing. In the servicing of the broach, undersized teeth can be easily removed and replaced with new teeth to extend the life of the entire broach assembly, and any one or more teeth involved in a crack-up or other tooth damage can also easily be replaced. As a further important consideration, the fact that the consequences of damage or error, either in manufacture, assembly or use, are limited to individual teeth rather than the entire stick, means that expensive but highly desirable materials such as carbide can be used as the tooth material.

Accordingly, one object of the present invention is to provide a novel and improved tooth for a form broach.

Still another object of the present invention is to provide a novel and improved individual tooth for a form broach.

Still another object of the present invention is to provide a novel and improved individual tooth for a form broach in which the individual teeth may be assembled in a cooperating interlocking array.

Still another object of the present invention is to provide a novel and improved individual tooth for a form broach in which the consequences of error or damage in manufacture, assembly or use are restricted to only the particular tooth or teeth damaged thereby.

Other objects and advantages will be apparent and understood from the following detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS:

In the drawings, wherein like elements are numbered alike in the several figures,

FIG. 1 is a front view of a broach employing the individual tooth of the present invention, the view being shown partly broken to indicate that the teeth are adapted to be assembled in an array of substantial length.

FIG. 2 is a side view of the broach of FIG. 1.

FIG. 3 is a perspective view of a broach employing the individual teeth of the present invention, the view in FIG. 3 showing several teeth removed from an assembly for purposes of clarity in illustrating some of the details of the assembly.

FIG. 4 is a view showing retainer assembly structure for use with the individual teeth of the present invention.

FIG. 5 is a view showing mounting structure for use with the present invention.

FIG. 6 is a view, looking head on, of one of the teeth of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT:

Referring now to FIG. 1, a form broach 10 has a plurality of interlocking individual cutting elements in the form of tooth segments 12 extending along the greater part of the length of the broach. Not all of the teeth are shown in detail in FIG. 1, and the broach is shown broken along its length to indicate its extended length, but it will be understood that the individual tooth segments 12 are stacked one upon the other along the entire working length of the broach. The teeth depicted in FIG. 1 are roughing teeth with roughing cutting elements 14 mounted on the front ends of the teeth (see also FIG. 2). As can best be seen in FIG. 2, the cutting elements increase in size from left to right along the length of the broach so that the leftmost end of the assembly is the leading end in the broaching operation.

Viewing the assembly of FIG. 1 as lying on its side, the top surface of each tooth is provided with a V-groove or notch 16 along substantially the full length of the tooth, and the bottom surface of each tooth has a corresponding V-shaped projection 18 along substantially the full length of the tooth. The V- grooves preferably have an included angle of approximately 120 as depicted, and the exterior angle of each V-projection 18 is approximately 240 as depicted so that the V-projections 18 and the V-grooves l6 mate in complete interlocking arrangement. However, it will be understood that other angles could be used in this form of interlocking arrangement. As can best be seen in FIG. 2, the grooves 16 and the projections 18 extend along substantially the entire length of each individual tooth so that the interlocking conjunction between the teeth is present along the entire length of the teeth. Since one surface of each tooth is provided with a V projection and the other surface of the tooth is provided with a V-groove, each tooth, except the top and bottomteeth in the array, has a bottom V- projection mating and interlocking with a top V-groove in the next lower tooth, and the upper surface of each tooth has a V- groove mating and interlocking with a V-projection in the next upper tooth. The bottom surface of the lowest tooth and the top surfaceof the uppermost tooth do not mate with adjacent teeth, but they do mate and interlock with retaining structure as will be more fully described so that each tooth in the assembly is fully mated and interlocked at both upper and lower surfaces with appropriately shaped adjacent surfaces. Of course, it will be understood that the V-groove and V-projection arrangement could be reversed so that the projection is on the top surface of each tooth and the groove at the bottom surface of the tooth.

Still referring to FIGS. 1 and 2, and with further reference to FIG. 4, the stack of adjacent and interlocking individual cutting teeth is held together by retaining structure in the form of an interconnected lock block 20 at the top or forward end of the broach and a backup block 22 at the bottom or rear end of the broach. Lock block 20 has a V-projection at the bottom surface thereof to mate with the V-groove in the tooth segment to which it is adjacent, and backup block 22 has a V- groove in its top surface to mate with the V-projection from the tooth segment to which it is adjacent. Each tooth has a hole 24 therein near the root end of the tooth, the holes being in the same relative position in each tooth so that the. h oles cooperate to form a continuous passageway when the teeth are in alignment to form the broach. Lock block 20 and backup block 22 also have similarly positioned holes, and a tie rod 26 extends from lock block 20 through the roots of all of the teeth 12 and into backup block 22. Lock block 22 has a cylindrically shaped recess 28 and a pair of diametrically op posed side openings 30. A head structure attached to one end of rod 26 consisting of a cylindrical collar 32 and side wings 34 respectively fit in and engage recess 28 and side openings 30. The engagement of collar 32 and wings 34 in recess 28 and side openings 30 can also be clearly seen in the perspective view of FIG. 3. The other end of rod 26 has a threaded portion 36 which projects into a cylindrical recess 38 in backup block 22, and an elongated cylindrical set nut 40 is housed in recess 38 and screws onto threaded portion 36 to complete the retainer structure. The relative sizing of the parts is such that set nut 40 can be screwed tightly onto threaded portion 36 to urge the teeth, the locking block and the backup block together to exert an extremely high compression force along the entire broach assembly. Rod 26 is provided with a flat 42 which engages with a fixed pin 44. The engagement between pin 44 and flat 42 prevents twisting and torquing of rod 26 when nut 40 is being tightened. I

The retainer structure described immediately above secures the individual teeth in an assembled relationship and provides a substantial compression force to urge the teeth together. The V-groove interlocking between successive teeth then operates to prevent any relative movement or winking between the teeth so that the assembly has all of the effect of and the advantages of a stick broach without any of the disad' vantages thereof and without any of the disadvantages previously present in attempts at individual tooth assemblies.

Referring now to FIG. 3, a perspective is shown of a broach assembly in accordance with the present invention. Merely for purposes of illustration, some of the tooth segments have been omitted so that the construction of an individual tooth can be fully observed along with the relationship between the teeth. The cutting teeth shown in FIG. 3 are provided with the Christmas tree serrations 46 so that the broach shown in FIG. 3 is a finishing broach. Thus, it will be understood that the present invention can be employed with roughing broaches such as shown in FIG. 1 or finishing broaches such as shown FIG. 3; and it will also be understood that any desired successive variation in shape between successive teeth can be employed so that, for example, a transition could be made from roughing teeth at one end to intermediate teeth at the other end, or from intermediate teeth to finishing teeth, or even from roughing teeth to finishing teeth if the nature of the operation permitted.

The relationship of the individual teeth 12, both between themselves and with locking block 20 and backup block 22 and rod 26 and collar 32, can be clearly seen in FIG. 3. In addition, the extension of the V-groove 16 along substantially the entire length of the tooth segments 12 can clearly be seen in FIG. 3 by virtue of the illustrative removal of some teeth, and it will be understood that the mating V-projection 18 (as seen in the tooth shown in FIG. 6) on the bottom of each tooth also extends along substantially the entire length of the tooth.

Referring now to FIG. 5, the assembled broach 10 would be mounted in a conventional ram body 48 for the broaching operation. In order to insure proper securing of the broach 10 in ram body 48, each tooth segment has a 45 V-notch 50 formed on one side thereof, and a correspondingly V-shaped clamping bar fits into notch 50 and is secured to the ram body by screw 50. The interaction between bar 52 and notch 50 forces the broach assembly against surfaces 56 and 58 in the ram body to securely retain broach 10 in the ram body. Thus, additional stability is achieved.

Although the foregoing discussion has been directed to a V- groove and V-projection interlock, it will be understood that the invention is not limited to this form of interlock. Any equivalent interlock contoured shape could also be employed to provide interlocking and support between adjacent inserts along their length, such as serrations along the length of the inserts, radial surfaces along the length of the inserts or tongue and groove along the length of the inserts.

From the foregoing description and discussion it can be seen that the present invention produces a practicable and effective segmented tooth form broach composed of individual tooth segments. Broach stability is insured and winking is eliminated by the V-groove and V-projection interlock between the teeth in the broach.

While a preferred embodiment has been shown and described, various modifications and substitutions may be made without departing from the spirit and scope of this invention. Accordingly, it is to be understood that this invention has been described by way of illustration rather than limitation.

What is claimed is:

l. A cutting element for a broach, the cutting element havmg:

a body with top and bottom surfaces and at least one contoured cutting surface between said top and bottom surfaces;

a contoured recess on one of said top and bottom surfaces;

and

a contoured projection on the other of said top and bottom surfaces;

said contoured recess and contoured projection extending along substantially the entire length of said body, including along substantially the full length of said cutting surface; said contoured recess and contoured projection being of interlocking shape.

2. A cutting element as in claim 1 wherein:

said contoured recess is a V-groove and said contoured projection is a corresponding V-projection.

3. A cutting element as in claim 2 wherein:

said V-groove has an angle of approximately 120 and said V-projection has an angle of approximately 240.

4. A cutting element as in claim 3 wherein:

said V-groove is on said top surface and said V-projection is on said bottom surface.

5. A cutting element as in claim 1 including:

an opening through said cutting element near the one end of said cutting element and through said top and bottom surfaces.

6. A cutting element for a segmented broach, the cutting element having:

a body with top and bottom surfaces and at least one contoured cutting surface between said top and bottom surfaces;

a contoured recess on one of said top and bottom surfaces, said contoured recess extending along substantially the entire length of said body, including along substantially the entire length of said cutting surface;

a contoured projection on the other of said top and bottom surfaces, said contoured projection extending along substantially the entire length of said body, including along substantially the entire length of said cutting surface, said projection and said recess being of mating shape to provide surfaces for complementary interengagement of adjacent cutting elements when a plurality of cutting elements are arrayed in a cutting array; and

an opening through said cutting element at one end thereof and through said top and bottom surfaces to receive a tie rod;

said cutting element being adapted to cooperate with a plurality of said cutting elements to form an array wherein a cutting element interlocks with an adjacent cutting element in the array through engagement between the top surface of one cutting element and the bottom surface of an adjacent cutting element.

7. A cutting element as in claim 6 wherein:

said contoured recess is a V-groove and said contoured projection is a corresponding V-projection 8. A cutting element as in claim 7 wherein:

said V-groove has an angle of approximately and said V-projection has an angle of approximately 240.

9. A cutting element as in claim 8 wherein:

said V-groove is on said top surface and said V-projection is on said bottom surface. 

1. A cutting element for a broach, the cutting element having: a body with top and bottom surfaces and at least one contoured cutting surface between said top and bottom surfaces; a contoured recess on one of said top and bottom surfaces; and a contoured projection on the other of said top and bottom surfaces; said contoured recess and contoured projection extending along substantially the entire length of said body, including along substantially the full length of said cutting surface; said contoured recess and contoured projection being of interlocking shape.
 2. A cutting element as in claim 1 wherein: said contoured recess is a V-groove and said contoured projection is a corresponding V-projection.
 3. A cutting element as in claim 2 wherein: said V-groove has an angle of approximately 120* and said V-projection has an angle of approximately 240*.
 4. A cutting element as in claim 3 wherein: said V-groove is on said top surface and said V-projection is on said bottom surface.
 5. A cutting element as in claim 1 including: an opening through said cutting element near the one end of said cutting element and through said top and bottom surfaces.
 6. A cutting element for a segmented broach, the cutting element having: a body with top and bottom surfaces and at least one contoured cutting surface between said top and bottom surfaces; a contoured recess on one of said top and bottom surfaces, said contoured recess extending along substantially the entire length of said body, including along substantially the entire length of said cutting surface; a contoured projection on the other of said top and bottom surfaces, said contoured projection extending along substantially the entire length of said body, including along substantially the entire length of said cutting surface, said projection and said recess being of mating shape to provide surfaces for complementary interengagement oF adjacent cutting elements when a plurality of cutting elements are arrayed in a cutting array; and an opening through said cutting element at one end thereof and through said top and bottom surfaces to receive a tie rod; said cutting element being adapted to cooperate with a plurality of said cutting elements to form an array wherein a cutting element interlocks with an adjacent cutting element in the array through engagement between the top surface of one cutting element and the bottom surface of an adjacent cutting element.
 7. A cutting element as in claim 6 wherein: said contoured recess is a V-groove and said contoured projection is a corresponding V-projection
 8. A cutting element as in claim 7 wherein: said V-groove has an angle of approximately 120* and said V-projection has an angle of approximately 240*.
 9. A cutting element as in claim 8 wherein: said V-groove is on said top surface and said V-projection is on said bottom surface. 